ERHIC with Self-Polarizing Electron Ring V.Ptitsyn, J.Kewisch, B.Parker, S.Peggs, D.Trbojevic, BNL,...
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Transcript of ERHIC with Self-Polarizing Electron Ring V.Ptitsyn, J.Kewisch, B.Parker, S.Peggs, D.Trbojevic, BNL,...
eRHIC with Self-Polarizing Electron Ring
V.Ptitsyn, J.Kewisch, B.Parker, S.Peggs, D.Trbojevic, BNL, USAD.E.Berkaev, I.A.Koop, A.V.Otboev, Yu.M.Shatunov, BINP, Russia
C.Tschalaer, J.B. van der Laan, F.Wang, MIT-Bates, USA D.P.Barber, DESY, Hamburg, Germany
The EIC w.r.t. Other Experimental Facilities
Large luminosity and high CM Energy makes EIC unique!
Variable CM energy enhancesits versatility!
TESLA-N
EIC Objectives
e-p and e-ions collisions 5-10 GeV electrons; 25-250 Gev protons; 100 Gev/u Au Luminosity:
L = (0.3-1)x1033 for e-p collisions
L = (0.3-1)x1031 for e-Au collisions
Polarized electron and proton beams Longitudinal polarization at collision point; 70% 35 nsec minimum separation between bunches
BRAHMS & PP2PP (p)
STAR (p)
PHENIX (p)
AGS
LINACBOOSTER
Polarized Proton in RHIC
Pol. Proton Source500 A, 300 s
GeVs
cmsL
50050
onPolarizati%70
102 2132max
Spin Rotators
Partial Siberian Snake
Siberian Snakes
200 MeV Polarimeter AGS Internal Polarimeter
Rf Dipoles
RHIC pC PolarimetersAbsolute Polarimeter (H jet)
2 1011 Pol. Protons / Bunch = 20 mm mrad
AGS pC Polarimeters
Strong AGS Snake
eRHIC collider layout
• e-ring is 5/16 of RHIC ring
• Collisions at one IP
• 28 MHz collision rate
• Unpolarized electron source
• Electron beam polarization by the synchrotron radiation
• e-ring lattice based on
”superbend” magnets
p
e2GeV (5GeV)
2-10 GeV
IP12
RHICp 50-250 GeVAu 100 Gev/u
Superbend magnet
Issues:• Accomodation of radiated power
(7MW radiated at 10 GeV)
• Orbit lengthening versus beam energy
B,T
0.15m
3m
321 Bpol 2
0.2
10GeV
5GeV
0.57
10GeV
5GeV
22BESRL
The desired balance:short polarization time at theacceptable level of synchrotron radiation losses
Flexible control of the beam emittance
Polarization time with superbend
• Magnet bending field scaled proportionally with energy
• The superbend control of polarization time.
8-15min polarization time is achievable.
3
51
pol
0
50
100
150
200
250
300
4 5 6 7 8 9 10 11
Electron energy, GeV
Po
lari
zati
on
tim
e, m
in
0
2
4
6
8
10
12
14
16
18
4 5 6 7 8 9 10 11
Electron energy, GeV
Po
lari
zati
on
tim
e, m
in
Luminosity and beam-beam limits
Round beams:
x=y , x=y for electrons
Matching of the e and p beam sizes is crucial.
Reasonably achievable values:
0.05
0.005
Electron emittance versus electron energyfor different superbend settings
Ee=10GeV
Ee=5GeV
e-co
ol z
one
• Required normalized emittances for Au: 5-8 Pi mm*mrad at 5-10 GeV electron energies;
The cooling is required.
• Cooling of the proton beam is required for proton energies below 200 GeV
• Electron cooling system for RHIC is being developed.
0
10
20
30
40
50
60
70
4 6 8 10
Energy, GeV
Em
itta
nc
e, m
m m
ura
dBeam emittance control
Main beam parameters 2
Parameters e-ring
ion ring
p Au
C, m 1022 3833
E, GeV 5–10 250 100/u
nb 96 360
Nb 11011 11011 1109
I, Arms,mmrad
*, cm*, mm
0.4545–25100.07–0.050.05
0.4517–9
270.07–0.05
0.005
L, cm-2 s-1 (0.5-0.9)1033 (0.5-0.9)1031
Polarization issues
• 0.5mm rms closed orbit error assumed.
• The correction scheme similar to the one used at HERA should solve the problem.
• Fast polarimeter for the on-line spin resonance corrections.
The possibility to accelerate polarized light ions: deutrons, tritium, 3He, 19F (E.Courant).The polarized sources development is required.
Depolarization from ring imperfections in the e-ring
Horizontal separation scheme Vertical separation scheme
IR Design
• IR development proceeds in close link with the detector design• Detector background and protection from synchrotron radiation issues
Spin rotator
e-ring: solenoidal spin rotator -> simplest solution• Perfect longitudinal polarization at 7.5GeV
~15% reduction at 5 or 10 GeV.
• Spin transparency conditions on optics
n
12
solenoid solenoid
quadsn
1
2
Rotator design
p-ring: Helical spin rotator like being used already at two RHIC experiments
Summary:
The design is based on the construction of a self-polarizing electron ring.
Polarized e-p and unpolarized e-ion beam collisions in the center of mass energy range of 30-100 Gev and at luminosities up to 0.9x1033 cm-2s-1 for e-p and 0.9x1031 cm-2s-1 for e-Au collisions.
The electron polarization time of 8-15min is achieved with superbend magnets.
The collider design could be realized using the present level of the accelerator technology.